Troposphere nitric oxide formation

Nitrous oxide (N2O) is an important greenhonse gas with a radiative forcing effect 310 times that of CO2 and a lifetime in the troposphere of approximately 120 years. Part of the N2O is converted to NO in the stratosphere, and so contributes to depletion of ozone. Nitric oxide (NO) is very reactive in the atmosphere and has a lifetime of only 1-10 days. It contribntes to acidification and to reactions leading to the formation of ozone in the troposphere, and so also to global warming. 

Nitrogen oxide (NOx) The result of photochemical reactions of nitric oxide in ambient air a major component of photochemical smog. It is a product of combustion from transportation and stationary sources and a major contributor to the formation of ozone in the troposphere and to acid deposition. 

Carbon monoxide is oxidized in the troposphere ((133) and (134)). With a high concentration of nitric oxide in the troposphere, reactions (135) and (136) take place. This sequence is a formation of ozone catalyzed by nitric oxide. If the nitric oxide concentration is too low, the perhydryl radicals decompose ozone to form hydroxyl radicals (136). Ozone and peroxyacylnitrates PAN are the major toxins of smog. Peroxyacylnitrates are formed from aldehydes in a reaction catalyzed by nitric oxide. 

Extrapolation to the K/T boundary requires consideration of the time scales of acid deposition. Nitric acid formation occurs rapidly by aqueous phase reaction of NO and NO2 with liquid water produced by tlie incident K/T bolide on both impact and infall of ejecta. For tlie quantities of NO produced by the K/T impact ( 10 5 moles), conversion to HNO3 occurred wiUiin days, assuming sufficient liquid water was available in the posl-K/T atmosphere. The nitric acid will form an acid rain of pH 0 for a liquid water content of 1 g/m (typical of tropospheric clouds) but will contain enough protons to weather only 3 x 10 moles of Sr, for Sr/(Ta -0.003 in soil and bedrock minerals. Sulfuric acid formation occurred on a time scale of years [7] due to the slow rate of gas phase SO2 oxidation. Spread evenly over 10 years, 10 moles of SO2 produced a global acid rain of pH —4, and released —3 x 10 moles of Sr. 

An important consequence of reaction [3.42] is that NzO plays a certain role in the chemistry of ozone formation. Although a small part of the nitric oxide formed in this way returns into the troposphere by slow diffusion (see later Fig. 15), the majority of NO molecules takes part in stratospheric chemistry as discussed in Subsection 3.4.3. This suggests that N20 arising from the use of nitrogen containing fertilizers may pose a threat to the stratospheric 03 layer. 

Liittke, I, Scheer, V, Levsen, K., Wunsch, G, Cape, J. N., Hargreaves, K. X, Storeton-West, R. L., Acker, K., Wieprecht, W. and B. Jones (1997) Occurrence and formation of nitrated phenols in and out of clouds. Atmospheric Environment 31, 2637-2648 Lymar, S. V, V. Shafirovich and G. A. Poskrebyshev (2005) One-electron reduction of aqueous nitric oxide a mechanistic revision. Inorganic Chemistry 44, 5212-5221 Maahs, H. G. (1983) Measurement of the oxidation rate of sulphur(IV) by ozone in aqueous solution and their relevance to SO2 conversion in nonurban tropospheric clouds. Atmospheric Environment 17, 341-345... 

Little of the nitric oxide (NO) emitted at ground level can reach the stratosphere because of the efficient precipitative scavenging of its oxidation products NO2 and HNO3. The presence of NO in the troposphere affects the formation of ozone, through the oxidation of carbon monoxide, methane and other hydrocarbons [14]. It is therefore conceivable that increasing industrial inputs of CO and NO in the atmosphere will lead to increasing levels of tropospheric ozone [14]. 

With regard to direct NOx formation in nuclear explosions, we consider two nuclear war scenarios. Scenario I is Ambio s reference scenario [3]. In this scenario bombs having a total yield of 5750 Mt are detonated. The latimdinal and vertical distributions of the 5.7 x 10 molecules of nitric oxide produced in these explosions are determined by the weapon sizes and targets projected for this scenario. Since most of the weapons have yields less than 1 Mt, most of the NOx is deposited in the troposphere, and the effect on the chemistry of the stratosphere is much less than if the bomb debris were deposited mainly in the stratosphere. The assumed NO input pattern for the Scenario I war is provided in Table 5.1. 

The last step in the current manufacture of adipic acid involves oxidation by nitric acid, which results in the formation of nitrous oxide (N2O) that is released into the atmosphere. Given that N2O has no tropospheric sinks, it can rise to the stratosphere and be a factor in the destruction of the ozone layer. It also acts as a greenhouse gas (see Section 8.4.1). 

The oxidation of N02 eventually leads to the formation of nitric acid and aerosol nitrate, which are deposited at the earth surface. The relevant oxidation pathways are indicated in Fig. 9-6. The following discussion deals first with observations of reaction intermediates then with tropospheric abundances of N02, PAN, and HN03/ aerosol nitrate, and finally with the budget of nitrogen oxides and their oxidation products in the troposphere. 

At high concentrations (>50ppbv ppbv = parts per billion by volume), O3 in the atmospheric boundary layer becomes a toxic pollutant that also has important radiative transfer properties. The production of nitric acid from NO influences atmospheric pH, and contributes to acid rain formation. In addition, the oxidation of NO to the nitrate (NO3) radical at night influences the oxidizing capacity of the lower troposphere. Determination of the magnitude and location of NO sources is critical to modeling boundary layer and free tropospheric chemistry. 

Fig. 2.26 The biogeochemical nitrogen cycle. A ammonia synthesis (man-made N fixation), B oxidation of ammonia (indnstrial prodnction of nitric acid), C fertilizer application, D formation of NO due to high-temperature processes, E Oxidation of N2O within the stratosphere, F oxidation of NO within the troposphere, G ammonia deposition and transformation into ammonium, H biogenic emission, I biogenic N fixation, K denitrification, L nitrification, M assimilation (biogenic formation of amino adds), N mineralization. RNH2 organic bonded N (e. g. amines).

Nitric acid, HNO3 0.1-2 ppb 70 ppt 50-130 ppt Continental air Marine air Free troposphere Oxidation of NO2, 180 Formation of NO3 aerosol Wet and Ay position 6d... 

Paul continued to make major contributions to stratospheric chemistry. For example, he explained how nitric acid clouds cause the Antarctic ozone hole. At the same time, he also turned his attention to the troposphere, which is the air layer that connects with the biosphere and where weather and climate take place. The troposphere is also prone to air pollution, while it is cleaned by oxidation reactions. The self-cleaning capacity relies on the presence of reactive hydroxyl radicals that convert pollutant gases into more soluble compounds that are removed by rain. The primary formation of hydroxyl radicals in turn is from ozone. While most ozone is located in the stratosphere, protecting life on Earth against harmful ultraviolet radiation from the Sun, a small amount is needed in the troposphere to support the self-cleaning capacity. While previous theories had assumed that tropospheric ozone originates in the stratosphere, Paul discovered that much of it is actually chemically formed within the troposphere. The formation mechanism is similar to the creation of ozone pollution in photochemical smog . 

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